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| physical (temperature, pH, osmotic pressure) |
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| Each bacterial species has its own particular minimum, optimum, and maximum growth temperatures |
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| lowest temperature a species will grow at |
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| temperature the species grows best at |
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| the highest temperature at which growth for a particular species is possible |
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cold loving microbes
can grow at 0c
Optimum temperature is high |
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moderate temperature loving microbes
Optimum growth temperature is 25 to 40c
Many pathogenic bacteria have an optimum temperature of about 37c, and are mesophiles |
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heat loving microbes
endospores are usually heat resistant
may survive heat treatment
optimum growth temperature is 50 to 60C |
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| Microbes that use molecular oxygen |
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| Microbes that do not use oxygen |
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| do not use oxygen for growth, but they can tolerate it and grow in the presence of oxygen |
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| aerobic growth, oxygen is required in concentrations lower than those in air, they are sensitive to superoxide free radicals and peroxides that they produce when in oxygen-rich conditions |
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| describes organisms that can tolerate high salt concentrations |
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| can use oxygen when it is present, but can still grow without oxygen by using fermentation or anaerobic respiration |
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| A microorganism that grows best at relatively high CO2 concentrations |
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| Identify ways in which aerobes avoid damage by toxic forms of oxygen |
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| Enzymes such as catalase and superoxide dismutase (SOD) neutralize toxic forms of oxygen |
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| is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life. |
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is one of the three major macromolecules (along with DNA and proteins) that are essential for all known forms of life.
Like DNA, RNA is made up of a long chain of components called nucleotides. Each nucleotide consists of a nucleobase (sometimes called a nitrogenous base), a ribose sugar, and a phosphate group. The sequence of nucleotides allows RNA to encode genetic information. All cellular organisms use messenger RNA (mRNA) to carry the genetic information that directs the synthesis of proteins. In addition, some viruses use RNA instead of DNA as their genetic material; Like proteins, some RNA molecules play an active role in cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is protein synthesis, a universal function whereby mRNA molecules direct the assembly of proteins on ribosomes. This process uses transfer RNA (tRNA) molecules to deliver amino acids to the ribosome, where ribosomal RNA (rRNA) links amino acids together to form proteins. |
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| A large molecule containing carbon, hydrogen, oxygen, and nitrogen; some proteins have a helical structure and others are pleated sheets |
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| The process in which genes are transferred from one bacterium to another as "naked" DNA in solution. The changing of a normal cell into a cancerous cell |
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| The transfer of DNA from one cell to another by a bacteriophage |
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| The external manifestations of an organism's genotype, or genetic makeup |
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| The genetic makeup of an organism |
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| Any change in the nitrogenous base sequence of DNA |
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| The transfer of genetic material from one cell to another involving cell-to-cell contact |
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| A small circular DNA molecule that replicates independently of the chromosome |
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suppress the growth of unwanted bacteria and encourage the growth of the desired organisms
Example is Sabouraud's dextrose agar. The pH 5.6 is selective for fungi that should outgrow most bacteria at this pH |
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used to distinguish colonies of the desired organism from other colonies growing on the same plate
Example is blood agar--it distinguishes hemolytic colonies from other colonies on the same plate. The blood makes it differential. Streptococcus pyogenes causes strep throat and is hemolytic (lyses red blood cells) |
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| Media that is both Selective and Differential |
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Mannitol Salt Agar: used to culture Staphyloccus aureus which has a high tolerance for sodium chloride; it can also ferment the carbohydrate mannitol into an acid. The NaCl makes it selective for halophiles because the NaCL discourages the growth of competing organisms while favoring the growth of halophiles such as S. aureus
Differential because you can distinguish those colonies that ferment mannitol from those that do not.
The reagents that make it differential are the mannitol and pH indicator
yellow--mannitol
red for non-mannitol |
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| Selective for Gram-negative enteric organisms. Bile salts and crystal violet make it selective because bile salt encourages enteric organisms and crystal violet inhibits the growth of gram-positive bacteria |
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| It is differential because it distinguishes lactose fermenters from non-fermenters. The reagents are lactose and a pH indicator. Colonies that can ferment lactose are red or pink, and can be distinguished from colorless colonies that do not ferment lactose |
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selective sort of increase numbers
an enrichment medium is usually liquid and provides nutrients and environmental conditions that favor the growth of a particular micobe, but not others.
Similar to selective media, but designed to increase the numbers of desired microbes to detactable levels |
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| exact chemical composition is known. It is used for the growth of chemoautotrophs and photoautotrophs, and in microbiological assays |
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| made up of nutrients including the extracts of yeast, meat, or plants, or digests of proteins. Their chemical composition varies slightly from batch to batch. Used for the growth of most chemoheterotrophic organisms |
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| Refers to the destruction of all forms of microbe life, including endospores. The most common method of sterilization is heating (steam under pressure or sterilizing gas) |
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| Limited heat treatment. because the heat required for absolute sterility of canned food would degrade the quality of food, food is heated enough to destory Clostridium botulinum endospores |
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| A resistant, dormant structure formed within a cell that protects a bacterium from adverse environmental conditions |
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| the destruction of vegetative pathogens only |
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| a chemical that destroys vegetative pathogens on living tissue |
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| the mechanical removal of microbes from a limited area |
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| used for treatment intended to lower microbial counts on eating and drinking utensils to minimize pathogen transmission from one user to another |
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| inhibits the growth and multiplication of bacteria, once the bacteriostatic agent is removed, growth can resume |
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| an object or area is free of pathogens; aseptic techniques are used to minimize contamination |
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| kills microorganisms by denaturing their enzymes. A disadvantage includes that heat resistance varies with different organisms |
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| lowest temperature that will kill all the microorganisms in a liquid suspension in 10mins |
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| minimum length of time to kill all bacteria in a liquid culture at a give temperature |
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| the time, in minutes, it takes to kill 90% of the population of bacteria at a given temperature |
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| kills microorganisms primarily by protein denaturation (involving the breakage of hydrogen bonds) |
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advantages include that it kills vegetative forms of bacterial pathogens, most viruses, fungi, and their spores within about 10mins
disadvantage: endospores and some virsus are not destroyed this quickly
not always a reliable method of sterilization
used to wash dishes, basins, equipment
causes protein denaturation |
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steam under pressure
this is the preferred method of sterilization unless the higher temperatures or moisture can damage the material
steam must directly contat the material to be sterilized
higher the pressure, higher the temperature
causes protein denaturation |
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high-temperature short time HTST
a high temperature is used for a short time 72C for 15seconds to destory pathogens without altering the flavor of the food
ultra-high-temperature UHT treatment
140C for 3 seconds is used to sterilize dairy products
causes protein denaturation |
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| What is meant by equivalent treatments? |
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| As temperature is increased, much less time is needed to kill the same number of microbes. For this reason 63C for 30minutes and 72C for 15seconds could be considered equivalent treatments |
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direct flaming: involves burning contaminations
example is sterilizing an inoculationg loop with a Bunsen Burner |
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| very effective; also involves burning contaminants and can also be used to sterilize inoculating loop |
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| items are put in an oven at about 170c for 2hrs, causes oxidation. Very effective, but requires higher temperatures and longer periods of time than with moist heat. Mechanism of action is oxidation |
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involves pouring liquid or gas through a screen with small pores to filter out microorganism
advantage is that it can be used to sterilize heat-sensitive materials
the mechanism of action is the separation of the organisms from the suspending liquid
high-efficiency particulate air HEPA filters remove microorganisms larger than 0.3um in diameter
there are filters of different sizes down to about 0.01um |
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refrigerations 0-7c slows metabolic rate of microorganisms so they do not reporduce or synthesize toxins
decreased chemical reactions and changes in proteins |
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cultures are quick frozen between -50 and -92
the temperature causes the microbes to go dormant with decreased chemical reactions and changes in proteins
used for food, drug, and culure preservation |
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disrupts plasma membrane
denatures enzymes
disadvantages include its irritating qualities and odor |
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derivatives of phenol
cause disruption of lipid-containing plasma membranes
reduced irritating qualities
used on environmental surfaces, instruments, skin surfaces, and mucous membrane |
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derivatives of phenol
probably disrupt plasma membrane
used as a disinfectant in hand soap and skin lotions |
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include iodine and chlorine
antimicrobial activity is caused by hypochlorous acid from adding chlorine to water |
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| DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription |
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| Most bacteria do not have a membrane-bound nucleus, and their genetic material is typically a single circular chromosome located in the cytoplasm in an irregularly shaped body called the nucleoid.[63] The nucleoid contains the chromosome with associated proteins and RNA. The order Planctomycetes are an exception to the general absence of internal membranes in bacteria, because they have a double membrane around their nucleoids and contain other membrane-bound cellular structures.[64] Like all living organisms, bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from those of eukaryotes and Archaea.[65] |
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